Reducing agents antioxidants

Ascorbic acid is required for the synthesis of collagen. It is also a powerful reducing agent (antioxidant) and plays a part in intracellular oxidation-reduction systems, and in mopping up oxidants (free radicals) produced endogenously or in the environment, e.g. cigarette smoke (see Vitamin E). 

Uses are estimated to be manufacture of hydrosulfites and other chemicals, 40% pulp and paper, 23% food and agriculture (mainly corn processing), 14% water and waste treatment, 9% metal and ore refining, 6% oil recovery and refining, 4% and miscellaneous, including sulfonation of oils and as a reducing agent or antioxidant, 4% (270,271). 

Biochemical Functions. Ascorbic acid has various biochemical functions, involving, for example, coUagen synthesis, immune function, dmg metabohsm, folate metaboHsm, cholesterol cataboHsm, iron metaboHsm, and carnitine biosynthesis. Clear-cut evidence for its biochemical role is available only with respect to coUagen biosynthesis (hydroxylation of prolin and lysine). In addition, ascorbic acid can act as a reducing agent and as an effective antioxidant. Ascorbic acid also interferes with nitrosamine formation by reacting direcdy with nitrites, and consequently may potentially reduce cancer risk. 

Process 5, the conversion of hydroperoxides to alkoxy and hydroxyl radicals, can be interrupted by incorporation of a secondary antioxidant such as phosphites (e.g. Irgafos 168) or thioesters (e.g. Evanstab 12). These materials act as reducing agents, converting hydroperoxides to alcohols and themselves being converted to phosphates or sulfoxides, respectively (see Fig. 16). 

The basis to the chain breaking donor (CB—D) mechanism, which was the first antioxidant mechanism to be investigated, was laid down by the late 1940s [10-12]. Many reducing agents, e.g., hindered phenols and aromatic amines, which reduce the ROO to hydroperoxide in a CB—D step have already been empirically selected and used for rubbers and by this time also for the newer plastics industry (e.g., Table la, AO 1-8 and 9-12). The major mechanistic landmarks of the antioxi-... 

Erythorbic acid and sodium erythorbate are very safe products, widely used in the food industry as antioxidants and alternatives to vitamin C. In the water treatment industry, they are strong reducing agents that reduce metal oxides and hydroxides to their more soluble ferrous forms and promote the passivation of boiler waterside surfaces (magnetite formation). 

Antioxidants Reducing agents, such as vitamins C (ascorbic acid) and E (a-tocopherol), which scavenge toxic free radicals generated by oxidative reactions in the cell. 

Anti-foaming agent Antioxidant Substance which prevents or reduces foaming Substance which prolongs the shelf life of foodstuffs by protecting them against deterioration caused by oxidation, such as fat rancidity and colour changes... 

The study of oxidative damage has sparked a debate about the role that antioxidants might play in illness and aging. Antioxidants are reducing agents. They donate electrons to substances that have been oxidized, decreasing the damage caused by free radicals. Dietary antioxidants include vitamins C and E, beta-carotene, and carotenoids. 

---